THE CH^TOGNATHA. 



63 



Sagitta furcata, Steinliaus *. (PI. 4. figs. 7-15.) 



Characters. — Head comparatively small ; body thick ; neck not well marked in well- 

 preserved specimens ; no collarette. Body nearly equally thick throughout the middle 

 third, tapering gradually towards the head, very rapidly to the tail ; generally a marked 

 coustrictiou at the septum. Longitudinal muscles broad but thin ; lateral fields large ; 

 the body is therefore ti-ansparent and flabby, easily compressed in the tow-net. 



Posterior fin oval (elliptical), never quite triangular, about two-thirds on the body, 

 one-third on the tail ; its widest part well in front of the septum ; it ends at some 

 distance from the vesiculse seminales, but extends anteriorly nearly to the anterior fin. 

 Anterior fin widest ^posteriorly, but not so wide as the posterior fin ; it extends nearly to 

 the ventral ganglion. Tail-fin rounded and (? always) bilobed. 



Ventral ganglion small. Corona ciliata resembling that of hexaptera, but almost 

 entirely on the head, just reaching the neck. 



Jaws strong and markedly curved. Teeth long, strong, sharp. 



These characters do not in every respect agree with those given by Steinhaus, notably 

 as regards the fins. But from his mention of the " eigenthiimliche Runzelung der 

 Epidermis," I gather that his specimens, like the majority of mine, had suffered severely 

 in the tow-net. As I was in some doubt as to the identity of my specimens with 

 furcata, Dr. Krumbach, with some of Steinhaus's specimens before him, was kind 



* 0. Steinhaus : ' Die Verbreitung der Choetognathen im siidatlantischen iind indischen Ozean.' 

 SECOND SERIES. — ZOOLOGY, VOL. X. 11 



